Field of the Invention
The present invention relates to an image forming apparatus capable of changing an operating state, particularly to an image forming apparatus capable of changing an operating state between a normal mode and a power saving mode having power consumption lower than that of the normal mode.
Description of the Background Art
Examples of an electrophotographic image forming apparatus in which an image is formed by an electrophotographic system include an MFP (Multi Function Peripheral) having a scanner function, a facsimile function, a copying function, a function as a printer, a data communication function, and a server function, a facsimile machine, a copying machine, and a printer.
In a general image forming process where the electrophotographic system is adopted, a color (multi-color) image is formed on a recording sheet by the following method. A toner image is formed on a surface of an image bearing member by an electrostatic recording method, and the toner image is transferred to an intermediate transfer member and conveyed to a transfer unit. The transfer unit electrostatically transfers the toner image on the intermediate transfer member to a sheet that is conveyed from a sheet feed tray by a sheet conveying unit. Then the sheet is conveyed to a fixing device, and the toner image is fixed to the sheet by application of heat and pressure to the sheet. The sheet conveying unit discharges the sheet, to which the toner image is fixed, to a discharge tray.
In the case where office equipment, such as an MFP, particularly an image forming apparatus is not used for a long period of time, power feeding is partially turned off to cause an operating state of the image forming apparatus to transition to a power saving mode having low power consumption. On the other hand, in the case where a job is received or the image forming apparatus is manipulated, the image forming apparatus releases the power saving mode to transition to a normal mode. In the power saving mode, it is necessary that the power be fed to a CPU (Central Processing Unit) of a manipulation unit in order to detect an instruction to release the power saving mode, which is performed by a key manipulation of the manipulation unit of the image forming apparatus.
In order to further reduce the power consumption of the image forming apparatus, it is preferred that the power feeding be stopped in the power saving mode for the unit that detects the reception of the job or the manipulation of the image forming apparatus. Therefore, there is proposed a technology in which, in order to release the power saving mode (return the image forming apparatus from the power saving mode to the normal mode) without passing a current through the CPU of the manipulation unit, a human body of user who approaches the image forming apparatus is detected by low-power-consumption human body sensors, such as an infrared sensor and an electrostatic capacitance sensor, and the power saving mode of the image forming apparatus is released according to a human body detection signal of the human body sensor. In the technology, the image forming apparatus can return from the power saving mode even in a state where the CPU of the manipulation unit is turned off.
However, in the case where the human body detection signal of the human body sensor is used, there is a problem that the human body sensor is likely to falsely detect the human body to degrade reliability of the release of the power saving mode. For example, in an office where many persons exist, frequently the image forming apparatus is placed in a pathway of the office. In such cases, even when the person merely passes by in front of the MFP without using the MFP, sometimes the human body sensor falsely detects the human body and the image forming apparatus releases the power saving mode.
A manipulation panel for displaying information for the user and receiving the manipulation from the user is provided in image forming apparatuses, such as the MFP. Because an angle of the manipulation panel can be changed, sometimes the manipulation panel projects from the image forming apparatus depending on the angle. In the conventional image forming apparatus that releases the power saving mode using the human body detection signal of the human body sensor, in the case where the manipulation panel projects from the image forming apparatus, even if the person passes by in front of the image forming apparatus without touching the manipulation panel, sometimes the human body sensor detects the approach of the human body to release the power saving mode.
In order to prevent the problem, for example, it is conceivable that a detection sensitivity of the human body sensor is decreased to detect the human body only when the human body is located extremely close to the human body sensor. However, in this case, convenience is degraded for the user who wants to release the power saving mode as quickly as possible.
Document 1 below discloses a technology of being able to prevent the unintentional release of the power saving mode to some extent. In the technology disclosed in Document 1, the human body sensor that is driven in a time-sharing manner detects the human body, and a determination that the human body exists is made to release the power saving mode in the case where the human body sensor continuously outputs the human body detection signal for a specified time interval. Document 1: Japanese Patent Publication Laying-Open No. 2002-71833
According to the technology of Document 1, the false detection caused by the temporary approach of the human body to the image forming apparatus or the passage of the human body in front of the image forming apparatus can be prevented to some extent. However, there is a problem that the low reliability of the release of the power saving mode remains in the technology of Document 1. In the technology of Document 1, the human body sensor continuously outputs the human body detection signal for the specific time interval to release the power saving mode in the case where the person who has no intention to use the image forming apparatus stands in front of the image forming apparatus for the purpose of checking a document or chatting with another person. Desirably, the human body is not detected when the person merely stands in front of the image forming apparatus, but the human body is quickly detected when the human body of the user approaches the image forming apparatus in order to manipulate the image forming apparatus.
An angle at which a manipulation finger of the user approaches the manipulation panel changes depending on the angle of the manipulation panel. Accordingly, a range where the manipulation finger of the user is detected also changes according to the angle of the manipulation panel. However, in the conventional technology, because the detection range is set irrespective of the angle of the manipulation panel, sometimes the human body of the person who has nothing to do with the manipulation of the image forming apparatus is falsely detected.